Ninku, a Nintendo Game Boy title released in Japan, is likely an action or adventure game based on the manga series of the same name. It might have involved side-scrolling action, puzzle-solving, or other gameplay elements drawing inspiration from the manga's story and characters.  Pinpointing the exact developer and publisher requires additional research, as does a more detailed description of gameplay features.

Ninku (Japan)

Ninja Gaiden Shadow (USA)